1. Field
Embodiments relate to a sound quality evaluation apparatus configured to evaluate a quality of a sound which is output from a sound output apparatus and a method thereof.
2. Description of the Related Art
A sound output apparatus, such as a cellular phone, a camera, a camcorder, a MP3 device, a television, or an audio device, configured to output a sound is subject to a sound quality evaluation in a production/manufacturing process prior to a shipment.
A sound quality evaluation of a sound output apparatus is entirely performed according to a sensory test of a worker. Since such task is performed by a worker, a difference in sound quality of a sound output apparatus shipped by each different worker occurs, and a possibility of a hearing impairment, an increase of a fatigue from a workload, and a reduced productivity may be developed due to a repeated sound quality evaluation performed by a worker.
Since a subjective factor is intervened in such sound quality evaluation, a quantitative process of a sound quality evaluation is needed.
For such, a plurality of listeners were provided with a sound quality evaluation questionnaire, and with the result attained, a single sound quality evaluation model may be created, or with the audio signal measured may be converted into numeric figures such as THD (Total Harmonic Distortion), SNR (Signal to Noise Ratio), etc. through a frequency analysis method.
THD is a category configured to describe a performance of an amplifier, and examines a characteristic of an audio signal transmitted in the form of an electrical signal, not to examine a characteristic of an audio signal transmitted via air.
A method using a sound quality evaluation model is mainly used in a tuning process of an apparatus development stage, and a method to convert a sound quality evaluation category into numeric figures is used for a quality assurance of a finished product in a development or in a mass production stage.
Such sound quality evaluation of a sound output apparatus requires to be tested under a condition of a dead-sound chamber, and therefore, a loss of space/cost is resulted in by establishing a dead-sound chamber. Also, the sound quality evaluation in a dead-sound chamber may only be used for a sound output apparatus of a finished product or in a development stage, and therefore is less appropriate for a sound output apparatus at a production/manufacturing stage.
In addition, THD and SNR used for evaluating sound quality are limited in evaluating a sound quality of an apparatus.
In particular, even a fair quality sound output apparatus having small output capacity, such as a receiver of a mobile terminal or a speaker of a cellular phone or a camera, is with high THD, and therefore, the difference in THD between a fair quality apparatus and a defective apparatus is not clearly detected, thereby is limited in evaluating a sound quality.
In addition, SNR may be reliable if tested under a condition of a dead-sound chamber. However, in a condition where a surrounding noise is significant, such as a production/manufacturing site, the measured value may change according to the surrounding situation.
Therefore, an automated sound quality evaluation apparatus is needed in order to secure uniform sound quality of a sound output apparatus and to improve productivity of a sound output apparatus.